Field of the Invention
The present invention relates to telescopic suspension fork legs, such as fork legs used in conjunction with motorcycles and the like, and more specifically to a suspension fork leg with an inner tube, and an outer tube, and with a particular damping arrangement and a spring arrangement.
The telescopic suspension fork leg apparatus according to this disclosure can be used, for example, for the formation of a telescopic suspension fork, also abbreviated to “telefork,” which is used on a motorcycle or, for example, on a bicycle. Such a telescopic fork fulfils the function of guiding a front wheel of the vehicle in question, undertakes the task of suspension, and serves for damping when the vehicle moves over uneven areas of the roadway. The instant apparatus therefore provides that the spring movement subsides rapidly again, and also serves to support a braking moment which is built up upon the braking of the front wheel as a reaction moment, relative to the frame of the vehicle.
Background Art
To bring about a damping function for the damping of the oscillating movement of the inner tube and of the outer tube relative to each other, the damping arrangements of known suspension fork legs have bores, through which a damping fluid in the form, for example, of telescopic fork oil, can flow. To bring about a required characteristic in response to the respective specification of the rider (or respectively as a reaction to the condition of the roadway surface), a damping arrangement commonly possesses generally adjustable valve arrangements, via which the through-flow behavior of the damping fluid can be regulated.
When the damping fluid flows through the bores (or respectively the valves), very high local flow speeds are formed, which are so great that gas bubbles develop owing to a gaseous fluid phase, and cavitation often occurs. In order to avoid the formation of cavitation, the damping fluid is placed under high pressure, so that the formation even of gas bubbles can not occur.
A front wheel fork for a two-wheeled vehicle is known from publication WO 2008/085097 A1. In this known front wheel fork, a telescopic suspension fork leg is provided which has an inner tube and an outer tube and a damping arrangement and also a spring. The spring is arranged here in a first volume O1, while the damping arrangement has a second volume O2, which volumes are sealed hermetically with respect to each other. The damping arrangement of this known front wheel fork has two fluid volumes which are separated from each other, and which can be optionally connected with an equalizing reservoir. In this known type of front wheel fork, it is regarded as disadvantageous that the fluid in the first chamber, which holds the spring arrangement, can mix with the fluid in the damping arrangement. For this reason a third volume is provided, which preferably is filled with air and is intended to prevent a direct contact between the first volume O1 and the second volume O2.
By publication WO 2007/046750 A1 a front wheel fork is known which has a damping arrangement according to the so-called “closed cartridge” principle. This known front wheel fork here has a main spring arranged in the inner tube which is penetrated by a piston rod. On the piston rod, a damper piston is arranged which can carry out a back-and-forth movement in an inner tube of the damper arrangement. In so doing, the piston displaces a damping fluid, present in the damping arrangement, out from the interior of the inner tube via apertures which are connected with an annular space arranged coaxially to the interior of the damping tube. The annular space is in turn in fluid communication with a return flow chamber constructed in the inner tube of the damping arrangement, so that both the upper and the lower piston surface of the damping piston are in contact with the damping fluid. With the oscillating movement of the damping piston, the damping fluid is therefore conveyed from the compression chamber into the return flow chamber, wherein the compression chamber and the return flow chamber change over as a function of the stroke movement of the damping piston.
Such a system operating with parallel damping has the purported advantage that the damping fluid is constantly under pressure and in this way cavitation is prevented.
By German application DE 10 2007 028 634 A1, a shock absorber has become known with a piston rod and with a damping piston arranged thereon, which divides the working cylinder into two working chambers, wherein a balloon filled with gas is situated in one working chamber.
From EP 2 017 495 A1, a telescopic suspension fork leg has become known, and which possesses a damping piston in the region of a gripping clamp and has a separating piston which is movable relative to the piston rod.
By JP-2010-127327A, a telescopic suspension fork has become known with an outer tube and an inner tube arranged concentrically thereto. Inside the inner tube there is a gas volume and a separating piston, which is guided radially internally and sealed radially externally on the inner tube.
Known from publication US 2008/0105505 A1 is a telescopic suspension fork leg with an outer tube and with an inner tube provided concentrically thereto. On the inner tube, a separating piston is provided, sealed in both axial directions, which separates a gas volume from an oil volume and is acted upon by a spring arrangement.
Publication US 2010/0263971 A1 shows a damping arrangement which is filled with a magneto-rheological fluid and has a separating piston which seals the fluid with respect to a gas spring.
Finally, by publication US 2007/0056817 A1 a damping arrangement is known to have a first outer tube and an inner tube arranged coaxially thereto, and with a coaxial second outer tube, surrounding the inner tube, which second outer tube has a smaller external diameter than the first outer tube. Between the inner tube and the second outer tube a damping fluid can flow, which can act upon a damping piston, arranged inside the inner tube, on both piston surface sides. In the annular space region between the second and first outer tube, a separating piston is provided which seals a space, filled with a damping fluid, with respect to an air chamber and therefore is provided with sealing arrangements with respect both to the first and also to the second outer tube.
The disclosures of the foregoing publications are incorporated herein by reference.
In a further known telescopic suspension fork leg, an equalizing volume, which is provided for the damping fluid displaced by the damping piston, is provided outside the telescopic suspension fork leg and is sealed with respect to a gas spring via a sealing arrangement. Naturally, such a known telescopic suspension fork leg takes up a large installation space. If the telescopic suspension fork leg is arranged on a motorcycle, installation space is available only to a limited extent. If the equalizing volume is arranged separated from the telescopic suspension fork leg, then a fluid-conducting connection must be provided between the telescopic suspension fork leg and the equalizing volume, which can be constructed (for example) as a pressure hose. Such an external pressure hose is naturally liable to damage, which is disadvantageous in particular in motorcycles which are also moved on uneven ground.
If the additional equalizing volume is provided in the region between the damping pressure chamber and the gripping clamp, then this leads to a lengthening of the telescopic suspension fork leg in axial direction. As off-road sports motorcycles are in any case regularly equipped with large spring travels, such an axially longer embodiment of the telescopic suspension fork leg (and the telescopic fork provided therewith) leads to an undesirable rise in the motorcycle's seat height, entailing loss of comfort; further, the center of gravity of the motorcycle is raised. The same disadvantages are also produced when the equalizing volume is provided at the upper end of the telescopic suspension fork leg and in axial connection to the main spring.